Geology topics

Kenneth F. Tiffan

Publications and source records attributed to Kenneth F. Tiffan.

At least 19 recordsLinked to original sources

USGS2025

Gas bubble trauma progression and mortality in sculpin, threespine stickleback, and Northern pikeminnow

We examined the progression of gas bubble trauma (GBT) and associated mortality in sculpin ( Cottus spp.), threespine stickleback ( Gasterosteus aculeatus ), and Northern pikeminnow ( Ptychocheilus oregonensis ) exposed to three levels of total dissolved gas (TDG; 120, 125, and 130% saturation) in laboratory experiments. Sculpin were most sensitive to elevated TDG followed by stickleback and then pikeminnow, which were least sensitive. This was evidenced by GBT and associated mortality progressing fastest in sculpin and slowest in pikeminnow. GBT incidence and severity increased through time at all TDG levels tested, but relationships between severity and exposure time were statistically weak or nonexistent. GBT mortality progressed more rapidly as TDG increased in all species. Regional criteria developed to rank GBT in salmonids did not fully capture the incidence and severity of GBT in the three nonsalmonids we examined. Rather, using criteria that considered all areas of the fish provided more accurate data. The lateral line, body, dorsal fin, and pectoral fins were common locations of GBT in sculpin whereas in stickleback and pikeminnow, GBT was most common on the head and body. The proximate cause of GBT-related death was bubbles in the gills and heart, but unlike in other species, bubbles in these organs appeared rapidly just before the point of death. Our findings provide some of the first information on TDG effects on these little-studied species.

Oregon, Washington↗

USGS2024

Snake River Fall Chinook Salmon research and monitoring

In Chapter 1, we report on development and application of an integrated population model (IPM) for the natural-origin fall Chinook salmon population upstream of Lower Granite Dam. This year’s efforts represent the third update to the model. Initial efforts focused on generating juvenile and adult abundance estimates, with estimates of uncertainty, for informing the life-cycle model and estimating the effects of covariates on key demographic parameters. The goals of this year’s report are to 1) describe the modifications and advances made since the previous report, 2) to annually update and report the abundance estimates and other quantities used in the model, 3) to provide annual estimates of population parameters estimated by the IPM, and 4) to outline the next year’s tasks for advancing and/or applying the model. Since our last report on the life-cycle model, we have made a number of changes including: 1) incorporating jack abundance and age-structure data into the observation model, 2) changing smolt-to-adult survival (SAR) for subyearling and yearling to partial SARs that represent the joint probability surviving and entering the ocean at a given juvenile age, 3) combining age categories for rarely observed ages, 4) using scale data from unmarked fish to estimate age structure, and 5) generating composite life-cycle demographic parameters (cumulative capacity and productivity) from stage-specific parameters. We also generated juvenile abundance estimates, extended the model to include three additional brood years (1992– 2021), and ran the model to forecast returns to Lower Granite in 2022. For posterior medians of life stage-specific parameters, we estimated a mean productivity of 438 natural-origin juvenile recruits per female spawner, a capacity of 1.36 million juveniles, and a mean smolt-to-adult survival (SAR) of 1.2%. We detected strong density-dependent regulation, with juvenile recruits per spawner declining to about 50 juvenile recruits per female spawner at high spawner abundance. Across the entire life cycle, these stage-specific parameters resulted in a median cumulative intrinsic productivity of 1.93 adult female recruits per female spawner and a median equilibrium abundance of 2,851 female spawners (7,842 total spawners). Annual juvenile productivity varied from about 250–1,000 juveniles per spawner but displayed no temporal trends or patterns. For the three most recent brood years added to the model, recruits per spawner were higher than average but well within the range of uncertainty observed over the entire time series. In contrast to juvenile recruitment variability, SAR varied considerably among years and exhibited two periods of high survival (1996–2001 and 2007–2012) when SAR ranged from 2% to 6% and cumulative productivity ranged from 2 to 8 recruits per spawner. Partial SARs revealed that yearling outmigrants contributed substantially to the high SARs in the first high-survival period, but the second period was dominated by subyearlings. Yearlings contributed >30% to SAR in most years prior to 2007, and <30% since 2007. Our two-stage IPM provides a wealth of information about population dynamics affecting two key life-stage transitions (spawner to juvenile, and juvenile to spawner) centered on passage at Lower Granite Dam. By summarizing these stage-specific demographic parameters across the entire life cycle, this information will be useful for informing the recovery status of this threatened population. Whereas previous versions introduced hydrosystem and ocean covariates into the model, this phase of model development focused on solidifying the underlying model structure by introducing the concept of partial SARs and developing composite productivity and capacity as a function of underlying stage-specific parameters. Given this advancement, our next steps are to re-incorporate covariates into the model, specifically to understand how different factors affect partial SARs of subyearling and yearlings. Longer term model developments include:1) incorporating hatchery fish to explicitly estimate their survival as an alternative method for estimating natural-origin age composition, 2) expanding the model’s structure to include the three major spawning aggregates, 3) more explicitly modeling hydrosystem effects including transportation, and 4) using the model to assess retrospective and prospective management actions. In 2022, the U.S. Geological Survey (USGS) focused adult salmon survey efforts in the Snake River on deepwater redd searches and fish collection for parentage-based tagging (PBT) analyses. We use used a boat-mounted underwater video camera to count 99 deepwater redds at 16 of the 29 sites surveyed. Redd depths averaged 4.4 m. In conjunction with the Idaho Power Company, we collected genetic samples from 318 live fall Chinook salmon (Oncorhynchus tshawytscha) and 19 carcasses at 40 unique geographic locations that spanned 91 river kilometers. Eighty fish were collected at three sites (High Range [rkm 332.3], Dug Bar [rkm 315.4], and Three Creek [rkm 384.0]), which accounted for 23% of all collected fish in 2022. Most (333 fish) post-spawned salmon were collected from early to mid-November just after the peak of spawning. A summary of 2021 PBT results produced by the Idaho Power Company can be found in Appendix A.2. Beach seining and PIT tagging of subyearling fall Chinook salmon was conducted in Snake and Salmon rivers to obtain information on population metrics and growth as well as to provide data for ongoing life-cycle modeling. In the Snake River, we collected 7,496 subyearlings, tagged 4,139, and recaptured 502 (12.1%). Using 8-mm tags in 45–49-mm fish allowed us to represent an additional 25% of the juvenile population through PIT tagging beyond just using standard 9- and 12-mm tags. In the Salmon River, we captured 206 natural subyearlings with the majority (52%) of fish being captured at two sites: rkm 20 and 26. We tagged 145 subyearlings and recaptured 9 fish. Many of the subyearlings we tagged in the Snake River were detected passing Lower Granite Dam, but only 4 fish tagged in the Salmon River were detected. In total we detected 484 (11.3%) tagged fish at Lower Granite Dam, and detection rates varied by tag size and passage route. More subyearlings were detected passing via the removable spill weir (RSW) earlier in the season while more fish were detected passing through the juvenile fish bypass system (JBS) earlier in the season while more fish were detected passing via the removable spill weir (RSW) later in the season. In general, fish tagged with 12-mm PIT tags had higher detection rates than fish tagged with smaller tags. Survival to Lower Granite Dam was low and ranged from 0.22 to 0.36. Season-wide, growth of subyearlings was higher in the lower reach than in the upper reach of the Snake River.

Idaho, Oregon, Washington↗

USGS2023

Monitoring native nonsalmonids for the incidence of gas bubble trauma downstream of Snake and Columbia River dams during the spring spill season, 2022

In 2020, a new spill program was implemented to aid the downstream passage of juvenile salmonids at mainstem dams on the Snake and Columbia rivers. Under this program, the total dissolved gas (TDG) cap was increased to 125% and monitoring of native nonsalmonids for gas bubble trauma (GBT) became a requirement. The primary objective of this work was to measure the incidence and severity of GBT in native nonsalmonids resulting from increased juvenile fish passage spill and associated levels of TDG during the spring spill period. Native nonsalmonids were collected downstream from Bonneville, McNary, Ice Harbor, and Lower Granite dams and examined for the incidence and severity of GBT in 2022. Fish were collected at each location weekly (4 April to 13 June) during the spring spill period by backpack electrofishing and beach seining. Washington and Oregon state water quality agencies established minimum and target sample sizes for monitoring, but the minimum sample size of 50 fish and target sample size of 100 fish were not met in all weeks at individual projects due to high water flows and resulting low fish collections. Collected fish were examined for GBT according to the criteria and protocol established for the regional smolt monitoring program (SMP). Overall, GBT incidence and severity rankings were low and did not exceed the thresholds that would have triggered changes to the spill program. Using SMP criteria, maximum weekly GBT incidences were 1.9% downstream from Bonneville Dam, 8.6% downstream from McNary Dam, 7.7% downstream from Ice Harbor Dam, and 3.4% downstream from Lower Granite Dam. In contrast to 2021, several species showed signs of GBT in 2022, and GBT was commonly observed in fins and body locations other than the unpaired fins and eyes (i.e., SMP criteria). In general, the observed signs of GBT according to SMP criteria were not severe (i.e., ranks 1 and 2). Although TDG reached the gas cap, particularly late in the spring spill season, GBT incidence rates were not high probably due to factors such as habitat-related variability in TDG, species composition and varying tolerance to high TDG, low power to detect GBT incidence at small sample sizes, and unknown exposure history.

Oregon, Washington↗

USGS2022

Backpack electrofishing does not contribute to external signs of gas bubble trauma in sculpins

We exposed prickly sculpin Cottus asper and reticulate sculpin Cottus perplexus to electroshock and sham treatments in a controlled laboratory setting to determine if backpack electrofishing contributed to or exacerbated external signs of gas bubble trauma (GBT) in fish exposed to elevated total dissolved gas (TDG) levels. Fish were exposed to 115, 120 and 125% TDG (measured as percent of saturation) for various amounts of time (24–144 h) then subjected to a 5-s electroshock or sham treatment of no electroshock. Fish were examined to determine the incidence of GBT pre- and post-treatment, and all aspects (i.e., dorsal, ventral, left and right sides) of each fish were photographed. Across all TDG levels in all trials, no sculpin showed any change in GBT incidence following treatment. Analysis of GBT signs evident in photographs of 68 fish found no evidence of change in mean pre- and post-treatment gas bubble sizes in fish in any TDG trial, nor were any new gas bubbles found following treatment. We are aware of no physiological mechanism by which backpack electrofishing can cause GBT in sculpin, and as such, we believe using this gear should not increase GBT incidence rates in sculpin.

Aquaculture, Fish and Fisheries↗

USGS2021

Performance of subyearling fall Chinook salmon tagged with 8‐, 9‐, and 12‐mm passive integrated transponder tags in the Snake River

Inferences based on tagged individuals from a population are limited in part by the minimum size of fish that can be tagged. Smaller tags allow a greater proportion of a population to be represented by tagging and should reduce potential tag effects on fish performance. We evaluated different performance metrics of juvenile fall Chinook Salmon Oncorhynchus tshawytscha tagged with 8‐, 9‐, and 12‐mm PIT tags in the Snake River. We did not find evidence that posttagging mortality of 45–49‐mm‐FL fish tagged with 8‐mm tags was higher than the posttagging mortality of larger fish tagged with 9‐ and 12‐mm tags. The incisions of fish tagged with 8‐mm tags using 14‐guage needles healed faster than those of fish tagged with larger tags using 12‐guage needles. For individuals that received 8‐mm tags, growth in length and mass was higher for 45–49‐mm fish than for 50–59‐mm fish and 60‐mm and larger fish. Growth of the larger size‐classes (50–59 and ≥60 mm) was also generally higher for those tagged with 8‐mm tags compared to those tagged with 9‐ and 12‐mm tags, respectively. There were no strong relationships between tag burden (i.e., tag weight expressed as a percentage of fish weight) at the time of tagging and growth metrics for any tag size or fish size‐class. Releases made to compare the detection efficiency of the three tag types in the juvenile fish bypass at Lower Granite Dam, Washington, showed that 99–100% of all fish were detected. Survival of fish from rearing areas to Lower Granite Dam generally increased with fish size and varied by year, but there was no strong evidence of a tag size effect. The 8‐mm PIT tag allowed us to represent a larger portion (i.e., 6.2–24.1%) of the subyearling fall Chinook Salmon population in the Snake River without compromising fish performance or detectability at the dam.

Washington↗

USGS2021

Monitoring native, resident nonsalmonids for the incidence of gas bubble trauma downstream of Snake and Columbia River Dams, 2021

In 2020, a new spill program was implemented to aid the downstream passage of juvenile salmonids at mainstem dams on the Snake and Columbia rivers. Under this program, the total dissolved gas (TDG) cap was increased to 125% and monitoring of native, resident nonsalmonid (NRN) fishes for gas bubble trauma (GBT) became a requirement. The primary objective of this work was to measure the incidence and severity of GBT in NRN fishes resulting from increased juvenile fish passage spill and associated levels of TDG during the spring spill period. A secondary objective was to measure the incidence of GBT in incidentally collected juvenile salmonids when NRN sample size targets were met. NRN fishes were collected downstream from Bonneville, McNary, and Ice Harbor dams and examined for the incidence and severity of GBT in 2021. Fish were collected at each location weekly (6 April to 17 June) during the spring spill period by backpack electrofishing and beach seining. Washington and Oregon state water quality agencies established minimum and target sample sizes for monitoring, and in all weeks the minimum sample size of 50 fish was met and in most weeks the target sample size of 100 fish was met. Collected fish were examined for GBT according to the criteria and protocol established for the regional smolt monitoring program (SMP). Overall, GBT incidence and severity rankings were low and did not exceed the thresholds that would have triggered changes to the spill program. Using SMP criteria, weekly GBT incidences ranged from 0 to 1.0% downstream from Bonneville Dam, 0 to 6.2% downstream from McNary Dam, and 0 to 1.9% downstream from Ice Harbor Dam. Except for one three-spined stickleback (Gasterosteus aculeatus) collected downstream of Bonneville Dam, the only NRN species that showed signs of GBT was sculpin spp. GBT was observed in sculpin in body locations other than the unpaired fins and eyes (i.e., SMP criteria). If GBT incidence in all areas on the fish (i.e., paired fins, unpaired fins, eyes, body) are combined, then weekly GBT incidence rates increase and range from 0 to 4.3% downstream from Bonneville Dam, 0 to 15.4% downstream from McNary Dam, and 0 to 4.7% downstream from Ice Harbor Dam. This illustrates the effect of using different criteria to determine the incidence of GBT in NRN fishes. It also shows how the proportion of a species in a sample that is more prone to show GBT can influence GBT incidence rate. On a number of occasions, incidental catch of subyearling fall Chinook salmon were examined for GBT downstream of Bonneville Dam but none showed any signs. The DG was generally below 120% and never reached the 125% gas cap during the spring spill season, which may be why GBT incidence rates were so low as past research has shown that GBT signs in NRN fishes are relatively low below this TDG level.

Oregon, Washington↗

USGS2020

Impact of smallmouth bass predation on subyearling fall Chinook salmon over a broad river continuum

Smallmouth bass ( Micropterus dolomieu ) predation on subyearling fall Chinook salmon ( Oncorhynchus tshawytscha ) was examined in the Snake River (USA) to identify seasonal and habitat-related changes in bass diets, and associated subyearling consumption and loss in various riverine and impounded reaches. Smallmouth bass diets reflected opportunistic foraging that at times showed predation on subyearlings is influenced by the consumption of other prey such as crayfish, sand roller ( Percopsis transmontana ), and smaller invertebrates. Estimated loss of subyearlings was influenced by bass abundance and consumption rates. The highest bass abundances (> 1,000 bass/river kilometer) were observed in the upper reach of Hells Canyon early in April and May, and in Lower Granite Reservoir. Peak consumption rates of subyearlings (≥ 0.12 subyearlings/bass/day) occurred in the upper reach of Hells Canyon during May and in most reservoir reaches in June. Predation losses accumulated evenly along the river continuum from riverine to reservoir habitats. We estimated that 869,371 subyearlings could be lost to smallmouth bass predation between riverine production areas and Lower Granite Dam in a given year. To provide a context for this estimated loss, we provide an illustration of its potential effect on the adult population. Assuming no juvenile mortality occurred downstream of the dam and depending on smolt-to-adult return rates, this represented up to 3.9–16.0% of the potential adult run that could have returned to Lower Granite Dam had no subyearling predation by smallmouth bass occurred upstream of the dam. Although this study was limited by a number of assumptions and constraints, it does provide an illustration of how predation affects juvenile and adult salmon loss over a broad, changing river landscape.

Idaho, Oregon, Washington↗

USGS2019

Fall Chinook salmon (Oncorhynchus tshawytscha), sand roller (Percopsis transmontana), and smallmouth bass (Micropterus dolomieu) interactions in a Snake River reservoir: A tale of three species

We studied some of the relationships between federally listed fall Chinook Salmon, Oncorhynchus tshawytscha , endemic Sand Roller, Percopsis transmontana , and non-native Smallmouth Bass, Micropterus dolomieu , in Lower Granite Reservoir on the Snake River. Because of its recent reappearance and population increase, the Sand Rollers could be filling the role of a “native invader” in the reservoir food web. We speculated that Sand Rollers could either negatively affect fall Chinook Salmon by potentially competing with them for resources in shoreline habitats or, alternatively, benefit the salmon by providing a buffer against Smallmouth Bass predation. Nighttime beach seining showed that habitat use by fall Chinook Salmon and Sand Rollers overlapped completely in spring when both species were present along shorelines. Diet data from stomach samples also showed high overlap, but data on stable isotopes of 13 C and 15 N suggested that each species could be obtaining much of their dietary energy from different reservoir locations. Although habitat and diet overlap are evidence of competition, diel and spatial partitioning of resource use between fall Chinook Salmon and Sand Rollers may act to reduce potential competition. Analyses of Smallmouth Bass diets showed that fall Chinook Salmon and Sand Rollers comprised the majority of prey fish consumed by bass. Across years, as Smallmouth Bass increased their consumption of Sand Rollers (range 0.219 to 0.392 fish smallmouth -1 day -1 ), they decreased their consumption of fall Chinook Salmon (range 0.114 to 0.050 fish smallmouth -1 day -1 ). The greatest effect Sand Rollers may have on fall Chinook Salmon in Lower Granite Reservoir is to serve as a buffer against Smallmouth Bass predation.

Idaho, Washington↗

USGS2019

Research, monitoring, and evaluation of emerging issues and measures to recover the Snake River fall Chinook Salmon ESU

The portion of the Snake River fall Chinook Salmon Oncorhynchus tshawytscha ESU that spawns upstream of Lower Granite Dam transitioned from low to high abundance during 1992–2018 in association with U.S. Endangered Species Act recovery efforts and other federally mandated actions. This annual report focuses on (1) numeric and habitat use responses by natural- and hatchery-origin spawners, (2) phenotypic and numeric responses by natural-origin juveniles, and (3) use of a small unmanned aerial system (sUAS) to search for fall Chinook salmon redds and carcasses. Spawners have located and used most of the available spawning habitat and that habitat is gradually approaching redd capacity. Timing of spawning and fry emergence has been relatively stable, but effects of density dependence are evident in juvenile life stages. Apparent abundance of juvenile fall Chinook salmon has increased and we noted the following responses: parr dispersal from riverine rearing habitat into Lower Granite Reservoir has become earlier; growth rate (g/d) and dispersal size of parr declined; and passage timing of smolts from the two Snake River reaches has become earlier and downstream movement rate faster. These findings coupled with stock-recruitment analyses presented in this report provide evidence for density-dependence in the Snake River reaches and in Lower Granite Reservoir that was influenced by the expansion of the recovery program. The long-term goal is to use this information in a comprehensive modeling effort to conduct action-effectiveness and uncertainty research and to inform Fish Population, Hydrosystem, Harvest, Hatchery, and Predation and Invasive Species Management Research, Monitoring, and Evaluation (RM&E). In 2018, the U.S. Geological Survey (USGS) searched 10 shallow-water spawning sites and 25 deepwater spawning sites in conjunction with the Idaho Power Company (IPC). A total of 103 redds were counted at shallow-water sites and 61 redds were counted at deepwater sites. We recovered 17 carcasses and 13 live fish, which were spawned out, and collected biological information and tissue samples that are currently being analyzed for parentage to determine the percentage of hatchery-origin spawners on the spawning grounds.

Idaho, Oregon, Washington↗

USGS2019

Snake River fall chinook salmon life history investigations, 2018 annual report

The following report is divided into three sections each of which describes work conducted by different project cooperators. Chapter One describes smallmouth bass (Micropterus dolomieu) predation on subyearling fall Chinook salmon (Oncorhynchus tshawytscha) in Lower Granite Reservoir in 2018. Smallmouth bass abundance increased seasonally in shoreline habitats and was highest in the lower reach of the reservoir (1,239 fish/km of shoreline). Abundance ranged from 40,743 to 81,595 in 2018. We examined the relationship between smallmouth bass predation and subyearling habitat suitability. Bass abundance was highest in “natural” habitat (i.e., habitat with natural substrate that was not deemed suitable for subyearlings) and fish were generally larger in habitat classified as “suitable” (i.e., habitat deemed suitable rearing) for subyearling Chinook salmon. Subyearlings were present in all habitat types sampled but their abundance was 2–3 times lower in the lower reach of the reservoir. Sand rollers (Percopsis transmontana)—a common prey of smallmouth bass—were present in greatest numbers in “suitable” habitat in the upper reach and “natural” habitat in the middle reservoir reach, but few were observed in the lower reservoir. The total loss of subyearlings to smallmouth bass predation in 2018 (120,023) was slightly less than one-half that of 2016 (266,988) and more than twice that of 2017 (47,830). Total sand roller loss in 2018 (149,106) was slightly more than one-half the losses estimated in 2016 and 2017. Chapter Two describes the feasibility of using stable isotopes of carbon and nitrogen to distinguish hatchery and natural origin subyearling fall Chinook salmon that were consumed by smallmouth bass. A discriminant function was fit from isotopic signatures and fork length from known-origin hatchery and natural subyearlings. The function had an overall correct classification rate of 97.2%. Of subyearlings consumed by smallmouth bass the function correctly classified 94.3% of hatchery fish but only 64.3% of natural fish based on fish origins that were validated with parentage-based tagging (PBT) analysis. Most of the fish consumed by smallmouth bass were of hatchery origin and most of those were of the spring/summer run early in the year and of the fall run later in the year. Based on analysis of known-origin hatchery fish collected at Lower Granite Dam through time following release, using stable isotopes as a discriminatory tool is probably only effective for about two weeks following release, but may have greater utility in unimpounded systems where fish emigrate seaward more quickly. The third section of this report is a Master’s Thesis that covers work conducted under contracts 46273 REL 14 and 79562. The first chapter of the thesis examined growth of subyearling fall Chinook salmon rearing in three sections of the Snake and Clearwater rivers and Lower Granite Reservoir. Growth and food consumption were highest in the reservoir section than in riverine sections, though growth was not significantly higher in the reservoir for the full duration of the study. Julian date was the strongest predictor of growth and consumption, and both growth and consumption decreased over the course of the study, even when accounting for allometric growth effects. Findings suggest that fish rearing in the reservoir section during their early growth period may have an ephemeral energetic advantage relative to fish rearing in natal river sections. The second chapter of the thesis examined the spatial variation in natal river rearing and downstream movement in Snake River fall Chinook salmon. Based on otolith analyses, natal origin was related to differential habitat use with fish from the Clearwater River accruing 48% of their freshwater growth in their natal river compared to 40% for Snake River fish. These differences were associated with different mean size at natal river exit and at ocean entry.

Idaho, Washington, Oregon↗

USGS2018

Post‐release predation mortality of age‐0 hatchery‐reared Chinook salmon from non‐native smallmouth bass in the Snake River

Release of age‐0 hatchery‐reared fall Chinook salmon, Oncorhynchus tshawytscha (Walbaum), in the Snake River resulted in up to 30‐fold increases in salmon consumption by non‐native smallmouth bass, Micropterus dolomieu Lacepѐde. In an upper river reach, smallmouth bass fed intensively during a release in May, but Chinook salmon consumption returned to pre‐release levels within 1–2 days as hatchery‐reared fish quickly emigrated downstream. The predation response during a June release located farther downstream was dissimilar. Chinook salmon consumption increased to a lesser extent (11‐fold), lasted several days (~4) and no changes in feeding intensity were evident. Estimated numbers of age‐0 hatchery‐reared Chinook salmon lost to short‐term predation varied by year and study reach and ranged from 12,007 (6.03% of those released) to 210,580 (14.6% of those released) fish. Short‐term, intense feeding by smallmouth bass can contribute significantly to mortality of hatchery‐reared fish and should be considered when supplementing populations with hatchery juveniles.

Idaho, Washington↗

USGS2018

Upstream migration and spawning success of Chinook salmon in a highly developed, seasonally warm river system

This review summarizes what is known about the influence of water temperature and velocity on the migration and spawning success of an inland population of Chinook salmon Oncorhynchus tshawytscha . Models are then developed and used to illustrate how migration and spawning success might change if temperatures and velocities increase under a future climate. The illustration shows the potential for moderate increases in temperature and velocity to reduce homing and increase energy expenditure. Those two outcomes would reduce the abundance, productivity, and diversity of the population studied. Under the future scenario illustrated, it would become difficult for fish management actions alone to recover conservation-reliant populations of inland Chinook salmon.

Columbia River basin↗

USGS2018

Migratory behavior and physiological development as potential determinants of life history diversity in fall Chinook Salmon in the Clearwater River

We studied the influence of behavior, water velocity, and physiological development on the downstream movement of subyearling fall‐run Chinook Salmon Oncorhynchus tshawytscha in both free‐flowing and impounded reaches of the Clearwater and Snake rivers as potential mechanisms that might explain life history diversity in this stock. Movement rates and the percentage of radio‐tagged fish that moved faster than the average current velocity were higher in the free‐flowing Clearwater River than in impounded reaches. This supports the notion that water velocity is a primary determinant of downstream movement regardless of a fish's physiological development. In contrast, movement rates slowed and detections became fewer in impounded reaches, where water velocities were much lower. The percentage of fish that moved faster than the average current velocity continued to decline and reached zero in the lowermost reach of Lower Granite Reservoir, suggesting that the behavioral disposition to move downstream was low. These findings contrast with those of a similar, previous study of Snake River subyearlings despite similarity in hydrodynamic conditions between the two studies. Physiological differences between Snake and Clearwater River migrants shed light on this disparity. Subyearlings from the Clearwater River were parr‐like in their development and never showed the increase in gill Na + /K + ‐ATPase activity displayed by smolts from the Snake River. Results from this study provide evidence that behavioral and life history differences between Snake and Clearwater River subyearlings may have a physiological basis that is modified by environmental conditions.

Idaho, Washington↗

USGS2018

Juvenile Chinook Salmon mortality in a Snake River Reservoir: Smallmouth Bass predation revisited

Predation by nonnative fishes has been identified as a contributing factor in the decline of juvenile salmonids in the Columbia River basin. We examined the diet composition of Smallmouth Bass Micropterus dolomieu and estimated the consumption and predation loss of juvenile Chinook Salmon Oncorhynchus tshawytscha in Lower Granite Reservoir on the Snake River. We examined 4,852 Smallmouth Bass stomachs collected from shoreline habitats during April–September 2013–2015. Chinook Salmon were the second most commonly consumed fish by all size‐classes of Smallmouth Bass (≥150 mm TL) throughout the study. Over the 3 years studied, we estimated that a total of 300,373 Chinook Salmon were consumed by Smallmouth Bass in our 22‐km study area, of which 97% (291,884) were subyearlings (age 0) based on length frequency data. A majority of the loss (61%) occurred during June, which coincided with the timing of hatchery releases of subyearling fall Chinook Salmon. Compared to an earlier study, mean annual predation loss increased more than 15‐fold from 2,670 Chinook Salmon during 1996–1997 to 41,145 Chinook Salmon during 2013–2015 (in reaches that could be compared), despite lower contemporary Smallmouth Bass abundances. This increase can be explained in part by increases in Smallmouth Bass consumption rates, which paralleled increases in subyearling Chinook Salmon densities—an expected functional response by an opportunistic consumer. Smallmouth Bass are currently significant predators of subyearling Chinook Salmon in Lower Granite Reservoir and could potentially be a large source of unexplained mortality.

Idaho, Washington↗

USGS2018

Smallmouth bass predation on subyearling fall Chinook salmon in Lower Granite Reservoir, 2016–2017

Predation by nonnative fishes is one factor that has been implicated in the decline of juvenile salmonids in the Pacific Northwest. Impoundment of much of the Snake and Columbia Rivers has altered food webs and created habitat favorable for species such as smallmouth bass Micropterus dolomieu. Smallmouth bass are common throughout the Columbia River basin and have become the most abundant predator in lower Snake River reservoirs (Zimmerman and Parker 1995). This is a concern for Snake River fall Chinook salmon Oncorhynchus tshawytscha (hereafter, subyearlings) that may be particularly vulnerable due to their relatively small size and because their main-stem rearing habitats often overlap or are in close proximity to habitats used by smallmouth bass (Curet 1993; Tabor et al. 1993). Concern over juvenile salmon predation spawned a number of large-scale studies to quantify its effect in the late 1980s, 1990s, and early 2000s (Poe et al. 1991; Rieman et al. 1991; Vigg et al. 1991; Fritts and Pearsons 2004; Naughton et al. 2004). Smallmouth bass predation represented 9% of total salmon consumption by predatory fishes in John Day Reservoir, Columbia River, from 1983 through 1986 (Rieman et al. 1991). In transitional habitat between the Hanford Reach of the Columbia River and McNary Reservoir, juvenile salmon (presumably subyearlings) were found in 65% of smallmouth bass (>200 mm) stomachs and comprised 59% of the diet by weight (Tabor et al. 1993). Within Lower Granite Reservoir on the Snake River, Naughton et al. (2004) showed that monthly consumption (based on weight) ranged from 5% in the upper reaches of the reservoir to 11% in the forebay. However, studies in the Snake River were conducted soon after Endangered Species Act (ESA) listing of Snake River fall Chinook salmon (NMFS 1992). During this time, fall Chinook salmon abundance was at an historic low, which may explain why consumption rates were relatively low compared to those from studies conducted in the Columbia and Yakima Rivers where abundance was higher (e.g., Tabor et al. 1993; Fritts and Pearsons 2004). We speculate that predation on subyearlings by smallmouth bass in the Snake River may have increased in recent years for several reasons. Since their ESA listing, recovery measures implemented for Snake River fall Chinook salmon have resulted in a large increase in the juvenile population (Connor et al. 2013). Considering that subyearlings probably now make up a larger portion of the forage fish population, it is plausible they should make up a larger portion of smallmouth bass diets. Second, migrating subyearlings delay downstream movement in the transition zones of the Clearwater River and Snake River for varying lengths of time (Tiffan et al. 2010), which increases their exposure and vulnerability to predators. Spatial overlap in locations of smallmouth bass and subyearlings that died during migration provides support for this (Tiffan et al. 2010). Finally, the later outmigration of subyearlings from the Clearwater River results in their presence in Lower Granite Reservoir during the warmest summer months when predation rates of smallmouth bass should be highest. In 2016 and 2017, we focused our smallmouth bass predation efforts in Lower Granite Reservoir downstream of the transition zones and the confluence area where we worked during 2012–2015. This report primarily covers results from 2017 but some results from 2016 are also included for comparison. Similar to past years, our first objective was to quantify smallmouth bass consumption rates of subyearlings, determine bass abundance, and describe bass diets. In addition, Tiffan et al. (2016a) posited that predation risk to subyearlings may be higher in shoreline habitats that are more suitable for smallmouth bass and lower in shoreline habitats that are more suitable for subyearlings. To test this hypothesis, our second objective was to examine the relationship between smallmouth bass predation and subyearling habitat suitability. Our final objective was to combine estimates of consumption with smallmouth bass abundance to derive estimates of total Chinook salmon losses to smallmouth bass for 2016 and 2017.

Idaho, Washington↗

USGS2017

Ecology of the Sand Roller (Percopsis transmontana) in a lower Snake River Reservoir, Washington

The Sand Roller ( Percopsis transmontana ), has not been abundant in the Snake River since it was first found in the system in the 1950s, but its population has apparently increased in recent years. As a result, we initiated a study to better understand its ecology in habitats of Lower Granite Reservoir. From November 2014 to October 2015, Sand Rollers were present along shorelines, with peak abundance being observed during spring months. Logistic regression analyses showed that Sand Rollers were more likely to be present in shoreline habitats at temperatures ≤18.4°C. Fish were found over a range of substrates, with the lowest odds of fish presence being associated with riprap, which is common in hydropower reservoirs. From length-frequency analysis, we suggest that Sand Roller spawning occurs primarily in May and early June. Assessment of Sand Roller diets found dipteran (chironomid) larvae and pupae were the most important prey consumed by all sizes of Sand Rollers, but Opossum Shrimp ( Neomysis mercedis ) were also prominent in diets of larger fish in shoreline and offshore habitats. At a time when the populations of so many native species are in decline, the increase of the Sand Roller population in the lower Snake River represents a positive, yet curious occurrence.

Washington↗

USGS2017

Ecology of the Opossum Shrimp ( Neomysis mercedis ) in a Lower Snake River Reservoir, Washington

The opossum shrimp Neomysis mercedis has expanded its range from the lower Columbia River upstream 695 kilometers into Lower Granite Reservoir where it is now very abundant. We studied Neomysis ecology in the reservoir during 2011–2015 to better understand the physical and biological factors that shape their distribution as well as their potential role in the food web. Benthic densities in offshore habitats ranged from 19 to 145 mysids m -2 in shallow (2–12 m) water and from 3 to 48 mysids m -2 in deep (> 12 m) water. Water velocity, depth, substrate, and seasonal interactions were important variables for explaining variation in Neomysis densities in offshore habitats. During spring, daytime densities in shoreline habitats (< 2 m deep) were variable, but nighttime densities generally decreased in summer following reproduction and as temperatures approached 23 °C. Neomysis were mainly collected from the water column during nighttime vertical tows in the downstream end of the reservoir when water velocities were low during summer and autumn. Reproduction occurred mainly in spring and early summer, but a second, smaller reproductive event was observed during autumn. The diet of Neomysis consisted primarily of detritus, rotifers, and copepods, but cladocerans were more prominent during summer and autumn. Physical factors like water velocity may have limited vertical migrations of Neomysis to feed in the water column and influenced use of different habitats in the reservoir. Neomysis are prey for a number of species, including juvenile salmon, but their relations are still largely unknown, and continued monitoring and research is warranted.

Washington↗

USGS2017

Snake River Fall Chinook Salmon life history investigations

Predation by nonnative fishes is one factor that has been implicated in the decline of juvenile salmonids in the Pacific Northwest. Impoundment of much of the Snake and Columbia rivers has altered food webs and created habitat favorable for species such as Smallmouth Bass Micropterus dolomieu . Smallmouth Bass are common throughout the Columbia River basin and have become the most abundant predator in lower Snake River reservoirs (Zimmerman and Parker 1995). This is a concern for Snake River Fall Chinook Salmon Oncorhynchus tshawytscha (hereafter, subyearlings) that may be particularly vulnerable due to their relatively small size and because their main-stem rearing habitats often overlap or are in close proximity to habitats used by Smallmouth Bass (Curet 1993; Tabor et al. 1993). Concern over juvenile salmon predation spawned a number of large-scale studies to quantify its effect in the late 1980s, 1990s, and early 2000s (Poe et al. 1991; Rieman et al. 1991; Vigg et al. 1991; Fritts and Pearsons 2004; Naughton et al. 2004). Smallmouth Bass predation represented 9% of total salmon consumption by predatory fishes in John Day Reservoir, Columbia River, from 1983 through 1986 (Rieman et al. 1991). In transitional habitat between the Hanford Reach of the Columbia River and McNary Reservoir, juvenile salmon (presumably subyearlings) were found in 65% of Smallmouth Bass (>200 mm) stomachs and comprised 59% of the diet by weight (Tabor et al. 1993). Within Lower Granite Reservoir on the Snake River, Naughton et al. (2004) showed that monthly consumption (based on weight) ranged from 5% in the upper reaches of the reservoir to 11% in the forebay. However, studies in the Snake River were conducted soon after Endangered Species Act (ESA) listing of Snake River Fall Chinook Salmon (NMFS 1992). During this time, Fall Chinook Salmon abundance was at an historic low, which may explain why consumption rates were relatively low compared to those from studies conducted in the Columbia and Yakima rivers where abundance was higher (e.g., Tabor et al. 1993; Fritts and Pearsons 2004). We speculate that predation on subyearlings by Smallmouth Bass in the Snake River may have increased in recent years for several reasons. Since their ESA listing, recovery measures implemented for Snake River Fall Chinook salmon have resulted in a large increase in the juvenile population (Connor et al. 2013). Considering that subyearlings probably now make up a larger portion of the forage fish population, it is plausible they should make up a large portion of Smallmouth Bass diets. Second, migrating subyearlings delay downstream movement in the transition zones of the Clearwater River and Snake River for varying lengths of time (Tiffan et al. 2010), which increases their exposure and vulnerability to predators. Spatial overlap in locations of Smallmouth Bass and subyearlings that died during migration provides support for this (Tiffan et al. 2010). Finally, the later outmigration of subyearlings from the Clearwater River results in their presence in Lower Granite Reservoir during the warmest summer months when predation rates of Smallmouth Bass should be highest. In 2016, we focused our efforts on Smallmouth Bass predation in Lower Granite Reservoir downstream of the transition zones and the confluence area where we worked during 2012–2015. Similar to past years, our first objective was to quantify Smallmouth Bass consumption rates of subyearlings, determine relative bass abundance, and describe bass diets. In addition, Tiffan et al. (2016a) posited that predation risk to subyearlings may be higher in shoreline habitats that are more suitable for Smallmouth Bass and lower in shoreline habitats that are more suitable for subyearlings. To test this hypothesis, our second objective examines the relationship between Smallmouth Bass predation of subyearlings and habitat suitability.

Idaho, Washington↗